This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Antagonism of the D2 family of dopamine receptors is critical for antipsychotic action and occupancy of central D2 receptors has been related a threshold for antipsychotic effect, as well as a threshold for extrapyramidal side effects (EPS). However, previous studies did not perform baseline measurements of D2 binding potential (Bmax) in the same cohort of patients, but rather relied on an age corrected estimate from a separate, mixed group of healthy subjects and drug na[unreadable]ve patients. We have completed our study of the relationship between dose, serum level and cerebrospinal fluid level in monkeys and are analyzing the results. We have completed our study of the central D2 occupancy of drug at different doses using serial PET scans.